1. Field of the Invention
The present invention relates to an image processing method and device.
2. Description of Related Art
Full color images can be ideally reproduced using three CMY primary colors of cyan, magenta, and yellow. However, when a so-called gray scale is reproduced using a balance of inks in the three primary colors of cyan (C), magenta (M), and yellow (Y), it is very difficult to create a gray scale with a perfect balance in all tones. Sometimes, the resultant gray scale can appear with coloring, or with insufficiently dense black color.
To produce a single black dot image, pixels in the three primary colors of cyan, magenta, and yellow are ejected onto a recording medium at the same dot image position. If the pixels are ejected at positions slightly shifted from one another, then the region around the subject dot position will have coloring other than black. As a result, a sufficiently black color cannot be attained.
For the above-described purposes, presently-used many image recording devices, such as full-color printers, normally record full-color images using ink in four colors including: black (K) in addition to the three primary colors of cyan, magenta, and yellow.
In this way, by using black color in addition to the three primary colors of cyan, magenta, and yellow, color images can be recorded with a proper black quality. However, when dots of black ink are ejected directly onto a light colored portion, the black dots will give the light colored portion a “rough” dot appearance, resulting in an unnaturally-looking color image.
United States Publication No. US-2001/0009463-A1 has proposed a method of reducing the “rough” dot appearance in the light colored portion.